It is known to provide agricultural crop harvesting machines, of the type which pick up crop from a windrow, with a cutting device which reduces the crop for further processing. It is also known to mount each of the knives for individual release or tripping against a biasing force so as to protect them from being damaged from obstacles or crop which produces high loads, and to provide a way of selecting all, none, or various numbers of the available knives for operation so as to vary the amount that the crop is reduced by the active knives.
DE 43 02 199 discloses one way of selecting the number of active cutting knives. However, this cutting device requires each knife to be individually locked out of operation, which is time consuming and is difficult to achieve in the cramped environment where the cutting device is mounted.
U.S. Pat. No. 6,050,510 discloses a way of selecting the number of active cutting knives wherein a plurality of knives can be locked out of operation according to a pre-selected arrangement by pivoting a blocking rod into a desired location and securing it there for blocking a pre-selected arrangement of knives. While this device does permit multiple knives to be blocked out at the same time, the mechanism for achieving this operation is relatively complex and does not act together with the structure for individually biasing the knives to form a compact arrangement.
U.S. Pat. No. 6,394,893 discloses a hydraulically controlled arrangement including individual hydraulic actuators for each of the cutting knives and a hydraulic control circuit arrangement for selecting various arrangements of active knives.
U.S. Pat. No. 6,594,983 discloses cutting blades which are individually associated with trip mechanisms including resiliently biased plates which permit the cutting blades to pivot into a non-working position in response to a pre-selected overload. A support and control member is associated with each cutting blade and is mounted in a rotatable fashion and aligned about an axis parallel to a rotation axis of the associated cutting blade. A control device releases selected support members, thereby allowing all or a number of the cutting blades to rotate into a non-cutting position.
The problem to be addressed by the present invention is that of providing a crop cutting device with a knife-selecting device of a relatively simple design which is easily operable for selecting the number of active knives, without affecting the operation of a safety trip mechanism associated with the knives.